Certain types of printing systems are adapted for printing images on large-scale substrates, such as for museum displays, billboards, sails, bus boards, banners, and the like. The substrate can be a web or mesh-like material. In some of these systems, the web is fed along its length into the printing system. A carriage which holds a set of print heads scans across the width of the web while the print heads deposit ink as the web moves.
In many systems, a web guide directs the web through the printing system. The web guides generally include multiple sections coupled together. Some of these sections can be heated to condition the web prior to printing and to dry off the ink solvents after the image is printed. Furthermore, the systems are usually provided with a mechanism which keeps the web under tension to prevent it from wrinkling or bunching up.
During the printing process, it is desirable to have the web move across a smooth outer surface of the web guide. Typically, the sections of the web guide when coupled together form joints with raised and/or indented regions. These joints can cause the web to bunch up or wrinkle. The present invention implements an assembly for coupling the various sections of a web guide of a printing system to provide a smooth guide surface.
In one embodiment, the assembly includes a threaded bolt that engages a threaded bore of a first dovetail nut. The assembly also includes a second dovetail nut with a bore through which a shaft of the bolt passes. Each dovetail nut has two tapered portions located on opposite sides of the bore of the respective nut. When the bolt/dovetail nut combination is assembled, the two dovetail nuts are located a distance apart so that the tapered portions of the two nuts define a pair of slots. To connect sections of the web guide together, each slot engages a flared connector of a respective section.
Some embodiments can include one or more of the following features. The slots can have the same shape as the flared connectors. The sections can be provided with T-slots which engage with T-connectors of the sections. In addition, at least one section can have a V-shaped edge which engages with a V-shaped groove of another section to form a joint.
The T-connectors, the threaded bolt, the first dovetail nut, and the second dovetail nut can be made of steel. The sections of the web guide as well as the T-shaped slots can be made of aluminum.
Related embodiments include a method of connecting together two or more sections of a web guide of a printing system. An edge of a first section is engaged with an edge of a second section to form a joint. The two sections are joined together with a coupling assembly, and the sections are secured to a base of the web guide with one or more connectors.
Some embodiments may have one or more of the following advantages. The coupling assembly provides an easy mechanism to join together various sections of the web guide. The assembly facilitates precisely aligning the edges of adjacent sections to minimize the existence of raised or indented surfaces. Accordingly, the web is able to move across a uniform and smooth surface of the web guide surface, which prevents the substrate from bunching up or wrinkling. The coupling assembly eliminates the need for de-wrinkling rolls or other devices which are used to de-wrinkle the web. The assembly also eliminates the need for guide rolls. The coupling assembly facilitates constructing the web guide as a monolithic effectively seamless structure for drying, guiding, and de-wrinkling the web. Since some of the components of the guide have the same shape, the number of shapes of the components is minimized.